This applications claims priority from Canadian Patent Application No. 2,326,362 filed on Nov. 20, 2000.
Not Applicable
The present invention relates generally to optical switches and in particular to an optical switch based on the angle to offset principle.
Optical matrix switches are commonly used in communications systems for transmitting voice, video and data signals. Generally, optical matrix switches include multiple input and/or output ports and have the ability to connect, for purposes of signal transfer, any input port/output port combination, and preferably, for Nxc3x97M switching applications, to allow for multiple connections at one time. At each port, optical signals are transmitted and/or received via an end of an optical waveguide. The waveguide ends of the input and output ports are optically connected across a switch interface. In this regard, for example, the input and output waveguide ends can be physically located on opposite sides of a switch interface for direct or folded optical pathway communication therebetween, in side-by-side matrices on the same physical side of a switch interface facing a mirror, or they can be interspersed in a single matrix arrangement facing a mirror.
Establishing a connection between a given input port and a given output port, involves configuring an optical pathway across the switch interface between the input ports and the output ports. One way to configure the optical pathway is by moving or bending optical fibers using, for example, piezoelectric benders. The benders associated with fibers to be connected bend the fibers so that signals from the fibers are targeted at one another so as to form the desired optical connection across the switch interface. The amount of bending is controlled based on the electrical signal applied to the benders. By appropriate arrangement of benders, two-dimensional targeting control can be effected. Another way of configuring the optical path between an input port and an output port involves the use of one or more moveable mirrors interposed between the input and output ports. In this case, the waveguide ends remain stationary and the mirrors are used for switching. The mirrors can allow for one-dimensional or two-dimensional targeting to optically connect any of the input port fibers to any of the output port fibers and vice versa.
An important consideration in switch design is minimizing switch size for a given number of input and output ports that are serviced, i.e., increasing the packing density of ports and beam directing units. It has been recognized that greater packing density can be achieved, particularly in the case of a movable mirror-based beam directing unit, by folding the optical path between the fiber and the movable mirror and/or between the movable mirror and the switch interface. Such a compact optical matrix switch is disclosed in U.S. Pat. No. 6,097,860.
However, this approach in designing optical switches is to attach an individual lens collimator to each individual input and output port in order to xe2x80x9cthrowxe2x80x9d the beam to the switching element and to the desired output port. For an Nxc3x97M switch with a high port count, for example, this is a time consuming and costly procedure not to mention loss non-uniformity due to varying optical path lengths.
In accordance with the present invention, it is advantageous to move away from the traditional xe2x80x9cbeam-throwingxe2x80x9d approach and move towards geometric and imaging optics, where elements having optical power, such as a minor or a lens or lens system, are used to image the entire input waveguide array to the beam directing means, the beams of which are then send through a switching core and finally imaged to the output waveguide array.
It is an object of this invention to provide a compact optical switch, modulator, attenuator, and/or blocker.
In accordance with the invention there is provided an optical switch comprising an input port for launching a beam of light into the optical switch, at least two output ports, each output port for selectively receiving a beam of light, an ATO element having optical power for providing an angle to offset transformation, and beam directing means for selectively directing a beam of light from the input port to a selected one of the at least two output ports along an optical path via the ATO element.
In accordance with an embodiment of the present invention, the ATO element is a mirror or a lens.
In accordance with a further embodiment of the invention, the beam directing means are substantially disposed near or at a focal plane of the ATO element. In accordance with one embodiment, the beam directing means is an array of micro-mirrors being optically coupled with the input port and any one of the at least two output ports. In accordance with a further embodiment, the beam directing means comprise a first array of micro-mirrors near or at a first focal plane and a second array of micro-mirrors near or at a second focal plane of the ATO element. The first array of micro-mirrors is for tilting the beam of light, said tilt being converted to a lateral displacement using the lens and imaged onto the second array of micro-mirrors for selectively redirecting the beam to any one of the at least two output ports.
In accordance with yet a further embodiment of the present invention, the beam directing means comprise input and output micro-mirrors, and wherein the beam directing means have a tilt with respect to light beams incident thereon for directing the light beams to an approximate center of an area occupied by respective output micro-mirrors.
In accordance with an embodiment of the invention, the ATO element has a focal length approximately equal to a near zone length or Rayleigh range of a beam of light incident on the ATO element. In this embodiment, the ATO element is employed for maintaining a radius of the beam of light on the beam directing means.
In accordance with a further embodiment of the present invention, the optical switch further comprises an imaging system for imaging a beam of light onto the beam directing means. The imaging system can comprise reflective or transmissive elements. In accordance with one embodiment, the imaging system comprises at least one lens, and in another embodiment it comprises a telecentric imaging system. If desired, the telecentric imaging system is an off-axis telecentric imaging system.
In accordance with yet another embodiment of the present invention the optical switch further comprises a micro-lens centered on an optical axis of the input port for increasing an optical filling factor by increasing a beam diameter of the beam of light.
In another embodiment of the invention, the optical switch further comprises optical fibers at the input port and the plurality of output ports. In order to increase an optical filling factor, a portion of a cladding of the optical fibers is etched, or alternatively the optical fibers are drawn at an elevated temperature to have a reduced diameter.
In accordance with another embodiment of the invention, a parallel projection is used for increasing the optical filling factor.
In accordance with the invention, there is further provided an optical switch comprising an input port for launching a beam of light into the optical switch, at least two output ports, each output port for selectively receiving a beam of light, an ATO element having optical power and for providing an angle to offset transformation, and beam directing means for selectively directing a beam of light from the input port to a selected one of the at least two output ports along an optical path via the ATO element, said beam directing means being disposed near or at a focal plane of the ATO element.
In an embodiment of the present invention the ATO element is a curved mirror or a transmissive lens.
The present invention provides for beam directing in a transmissive or reflective configuration.
In accordance with another aspect of the invention, there is provided an optical switch comprising an array of controllable deflecting elements for switching a beam of light, and an ATO element optically coupled with the array of controllable deflecting elements for providing an angle to offset transformation, said array of controllable deflecting elements being disposed near or at a focal plane of the ATO element, and wherein a switching is performed along an optical path via the ATO element.
In accordance with the present invention there is further provided a modulator, attenuator, and/or blocker comprising an ATO element having optical power.